A5065427968- Graphene research and applications
- Topological Materials and Phenomena
- Quantum and electron transport phenomena
- Surface and Thin Film Phenomena
- Electron and X-Ray Spectroscopy Techniques
- Magnetic properties of thin films
- Semiconductor materials and devices
- 2D Materials and Applications
- Ion-surface interactions and analysis
- Advancements in Battery Materials
- Advanced Condensed Matter Physics
- Ga2O3 and related materials
- Electronic and Structural Properties of Oxides
- Diamond and Carbon-based Materials Research
- Carbon Nanotubes in Composites
- GaN-based semiconductor devices and materials
- Magnetic and transport properties of perovskites and related materials
- Integrated Circuits and Semiconductor Failure Analysis
- Solid-state spectroscopy and crystallography
- Fullerene Chemistry and Applications
- Physics of Superconductivity and Magnetism
- Photocathodes and Microchannel Plates
- Perovskite Materials and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Silicon Nanostructures and Photoluminescence
Helmholtz-Zentrum Berlin für Materialien und Energie
2014-2023
St Petersburg University
2008-2021
Freie Universität Berlin
2013-2018
TU Dresden
2018
Institute of Physics
2008-2011
Deutsches Elektronen-Synchrotron DESY
2010
Voronezh State University
2010
Abstract Materials harbouring exotic quasiparticles, such as massless Dirac and Weyl fermions, have garnered much attention from physics material science communities due to their exceptional physical properties ultra-high mobility extremely large magnetoresistances. Here, we show that the highly stable, non-toxic earth-abundant material, ZrSiS, has an electronic band structure hosts several cones form a Fermi surface with diamond-shaped line of nodes. We also square Si lattice in ZrSiS is...
For the purpose of recovering intriguing electronic properties freestanding graphene at a solid surface, self-organized on Au monolayer Ni(111) is prepared and characterized by scanning tunneling microscopy. Angle-resolved photoemission reveals gapless linear $\ensuremath{\pi}$-band dispersion near $\overline{K}$ as fingerprint strictly Dirac crossing energy equal to Fermi (${E}_{F}$) within 25 meV meaning charge neutrality. Spin resolution shows Rashba effect $\ensuremath{\pi}$ states with...
We show by angle-resolved photoemission spectroscopy that a tunable gap in quasi-free-standing monolayer graphene on Au can be induced hydrogenation. The size of the controlled via hydrogen loading and reaches approximately 1.0 eV for coverage 8%. local rehybridization from sp(2) to sp(3) chemical bonding is observed X-ray photoelectron absorption allows determination amount chemisorbed hydrogen. formation completely reversible annealing without damaging graphene. Calculations dependent core...
Photoelectron spectroscopy in combination with piezoforce microscopy reveals that the helicity of Rashba bands is coupled to nonvolatile ferroelectric polarization GeTe(111). A novel surface band found and fingerprints a bulk are identified by comparison density functional theory calculations. As service our authors readers, this journal provides supporting information supplied authors. Such materials peer reviewed may be re-organized for online delivery, but not copy-edited or typeset....
We study the effect of Fe impurities deposited on surface topological insulator ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ by means core-level and angle-resolved photoelectron spectroscopy. The state reveals electron doping when is at room temperature hole with increased linearity low ($\ensuremath{\sim}8\text{ }\text{ }\mathrm{K}$). show that in both cases remains intact gapless, contradiction to current belief. Our results suggest can very well exist functional interfaces ferromagnets future devices.
Spin currents which allow for a dissipationless transport of information can be generated by electric fields in semiconductor heterostructures the presence Rashba-type spin-orbit coupling. The largest Rashba effects occur electronic surface states metals but these cannot exist under ultrahigh vacuum conditions. Here, we reveal giant effect ({\alpha}_R ~ 1.5E-10 eVm) on state Ir(111). We demonstrate that its spin splitting and polarization remain unaffected when Ir is covered with graphene....
Graphene is considered a candidate material for spintronics. Recently, graphene grown on Ni(111) has been reported to show Rashba effect which depends the magnetization. By spin- and angle-resolved photoelectron spectroscopy, we investigate preconditions such an Ni as well Co $\ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}$ larger $3d$ magnetic moment: (i) spin polarization or (ii) exchange splitting of $\ensuremath{\pi}$ states in normal emission geometry, (iii) Rashba-type spin-orbit...
The long-term stability of functional properties topological insulator materials is crucial for the operation future based devices. Water and oxygen have been reported to be main sources surface deterioration by chemical reactions. In present work, we investigate behavior states on Bi2X3 (X = Se, Te) valence-band core level photoemission in a wide range water pressures both situ (from 10–8 0.1 mbar) ex (at 1 bar). We find that no reactions occur pure water. itself does not chemically react...
In both experiment and theory, we demonstrate a novel mechanism of flattened band formation in honeycomb lattice bilayer.
At very high doping levels the van Hove singularity in π^{*} band of graphene becomes occupied and exotic ground states possibly emerge, driven by many-body interactions. Employing a combination ytterbium intercalation potassium adsorption, we n dope epitaxial on silicon carbide past singularity, up to charge carrier density 5.5×10^{14} cm^{-2}. This regime marks unambiguous completion Lifshitz transition which Fermi surface topology has evolved from two electron pockets into giant hole...
Reaction of single-walled carbon nanotubes (SWNTs) with hydrogen gas was studied in a temperature interval 400–550 °C and at pressure 50 bar. Hydrogenation observed for samples treated 400–450 about 1/3 atoms forming covalent C–H bonds, whereas treatment higher temperatures (550 °C) occurs as an etching. Unzipping some SWNTs into graphene nanoribbons is result hydrogenation °C. Annealing elevated conditions prolonged periods time (72 h) demonstrated to also nanotube opening, purification...
A photoemission study of the electronic structure a single graphene layer on nickel shows that electrons in with broken lattice symmetry still move like massless particles, contrary to what is expected.
The helical Dirac fermions at the surface of topological insulators show a strong circular dichroism which has been explained as being due to either initial-state spin angular momentum, orbital or handedness experimental setup. All these interpretations conflict with our data from Bi2Te3 depend on photon energy and several sign changes. Our one-step photoemission calculations coupled ab initio theory confirm change assign final-state effect. polarization photoelectrons, instead, remains...
In this work, we present a model of the surface states nonsymmorphic semimetals. These are derived from mass terms that lift high degeneracy imposed in band structure by bulk symmetries. Reflecting reduced symmetry at surface, bands strongly modified. This leads to creation two-dimensional floating bands, which distinct Shockley states, quantum well or topologically protected states. We focus on layered semimetal ZrSiS clarify origin its demonstrate an excellent agreement between DFT...
This paper reports spin-dependent valence-band dispersions of graphene synthesized on Ni(111) and subsequently intercalated with monolayers Au, Cu Bi. We have previously shown that after intercalation Au the dispersion π band remains linear in region point surface Brillouin zone even though system exhibits a noticeable hybridization between states d Au. also demonstrated giant spin–orbit splitting Au-intercalated which can reach up to ∼100 meV. In this we probe detail π–Au hybridized bands....
New developments in the field of topological matter are often driven by materials discovery, including novel insulators, Dirac semimetals and Weyl semimetals. In last few years, large efforts have been performed to classify all known inorganic with respect their topology. Unfortunately, a number suffer from non-ideal band structures. For example, bands frequently convoluted trivial ones, structure features interest can appear far below Fermi level. This leaves just handful that intensively...
Regardless of the widely accepted opinion that there is no Raman signal from single-layer graphene when it strongly bonded to a metal surface, we present spectra monolayer on Ni(111) and Co(0001) substrates. The high binding energy carbon these surfaces allows formation lattice-matched (1 × 1) structures where significantly stretched. This reflected in record-breaking shift G band by more than 100 cm–1 relative case freestanding graphene. Using electron diffraction photoemission...
Abstract Spin and pseudospin in graphene are known to interact under enhanced spin–orbit interaction giving rise an in-plane Rashba spin texture. Here we show that Au-intercalated on Fe(110) displays a large (∼230 meV) bandgap with out-of-plane hedgehog-type reorientation around the gapped Dirac point. We identify two causes responsible. First, giant effect (∼70 meV splitting) away from point and, second, breaking of six-fold symmetry at interface. This is demonstrated by strong...
The interface of graphene with ferromagnets is highly relevant for spintronics, because on Co(0001) shows a largely intact Dirac cone and strong hybridization Co $3d$ states breaking the sublattice symmetry that had been considered mutually exclusive. Here we show by spin- angle-resolved photoemission point are also spin polarized $(\ensuremath{\sim}\ensuremath{-}25%)$, which reinforces puzzling issue graphene-substrate interaction. problem solved our ab initio calculations (i) upper lower...
The formation of large polarons has been proposed as reason for the high defect tolerance, low mobility, charge carrier trapping, and nonradiative recombination rates lead halide perovskites. Recently, direct evidence large-polaron reported from a 50% effective mass enhancement in angle-resolved photoemission CsPbBr_{3} over theory orthorhombic structure. We present in-depth band dispersion measurements GW calculations, which to similar masses at valence maximum 0.203±0.016 m_{0} experiment...
Graphene grown catalytically on Ir(111) shows a large substrate-induced spin-orbit splitting of ${\ensuremath{\Delta}}_{\mathrm{so}}\ensuremath{\sim}50\phantom{\rule{0.28em}{0ex}}\mathrm{meV}$ in spin- and angle-resolved photoemission. Its origin is hybridization as revealed by gaps the $\ensuremath{\pi}$ band. Reducing growth temperature results very Dirac cone, which found to be geometric allows for structural identification rotated graphene phase. The this phase considerably smaller,...
We analyze the strong hexagonal warping of Dirac cone Bi$_2$Te$_3$ by angle-resolved photoemission. Along $\overline{\Gamma}$$\overline{\rm M}$, dispersion deviates from a linear behavior meaning that is warped outwards and not inwards. show this introduces an anisotropy in lifetime broadening topological surface state which larger along K}$. The result consistent with nesting. Based on theoretically predicted ground-state spin texture strongly cone, we propose spin-dependent scattering...
We reinvestigate the putative giant spin splitting at surface of ${\mathrm{SrTiO}}_{3}$ reported by Santander--Syro et al. [Nat. Mater. 13, 1085 (2014)]. Our spin- and angle-resolved photoemission experiments on fractured (001) oriented surfaces supporting a two-dimensional electron liquid with high carrier density show no detectable polarization in photocurrent. demonstrate that this result excludes while it is consistent unconventional Rashba-like seen band structure calculations reproduce...